1. Field of the Invention
The present invention relates to a polarized light emitting diode (LED). More particularly, the present invention relates to a polarized LED capable of emitting polarized light in the front direction thereof by forming a first grating layer on a quantum well layer and forming a second grating layer on a substrate.
2. Description of the Related Art
Since a thin film transistor liquid crystal display (TFT-LCD) is not a self-emissive device, it must use the light of a backlight unit (BLU) which is an additional light source. The amount of transmitted light is adjusted according to the movement of liquid crystal molecules in response to applied signal voltage. Here, a polarizing plate that only passes through light of one polarization is necessarily required in a display device in order to prevent interference or offset of the transmitted light.
Since the polarizing plate directly adjusts light, it plays an important role of adjusting the required characteristics (e.g. contrast, luminance) of LCD products.
As described above, an additional polarizing plate is necessary for completing LCD products. Accordingly, if LCD products are manufactured without using the additional polarizing plate, the highest production efficiency can be achieved.
Meanwhile, the light source of the BLU has mainly used a lamp such as a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (EEFL). Recently, an LED (point source) has been used as the light source. That is, various semiconductor light emitting devices such as LEDs and LDs (laser diodes) have been used as light sources for a display apparatus, an illumination apparatus, optical communication apparatus, memory apparatus and the like.
Among such semiconductor light emitting devices, there has been developed a light emitting device, in which a III-V group nitride thin film that includes at least three layers of P and N type III-V group nitride single crystal thin film layers and a light emitting layer having a quantum well structure is epitaxially-grown from a substrate such as a sapphire substrate, the P and N type III-V group nitride single crystal thin film layers being obtained by doping a component selected from the group consisting of gallium nitride (GaN), indium nitride (InN) and aluminum nitride (AlN) with N and P type impurities.
A light emitting device prepared in the form of a stack structure including an N-type semiconductor layer, a light emitting layer and a P-type semiconductor layer that mainly include at least one component selected from the group consisting of GaN, InN and AlN has been used as a light source for a signal generator, a backlight for liquid crystal displays and a general illumination that can be substituted for an incandescent lamp or a fluorescent lamp. In addition, the light emitting device may be used as a laser light source for a high capacity optical disk apparatus.
The LED has a simple structure for generating light for LCD products. At the present time, technology for generating polarized light by modifying or improving the structure of the LED has not been proposed.
If it is possible to generate polarized light by modifying or improving the structure of the LED, LCD products can be completed without using the polarizing plate. However, the technology as described above has not been presented.